Hypertension and Hypotension : Part -2

Hypertension and Hypotension

II. Hypotension

Hypotension is abnormally low blood pressure. Normal blood pressure is a reading around 120/80 mmHg (mmHg = millimeters of mercury, a unit for measuring pressure). Hypotension is blood pressure that is lower than 90/60 mmHg.

Some people have low blood pressure all the time. They have no signs or symptoms and their low readings are normal for them. In other people, blood pressure drops below normal because of some event or medical condition. Hypotension is a medical concern only if it causes signs and/or symptoms such as dizziness, fainting, or, in extreme cases, shock (a medical emergency resulting from insufficient blood supply).

II.1 Symptoms and Diagnosis

Symptoms

There are several types of hypotension. One type, chronic asymptomatic hypotension, happens in people who always have low blood pressure. They have no symptoms and need no treatment. Their low blood pressure is normal for them.

Other types of hypotension happen only sometimes, when blood pressure suddenly drops too low. The symptoms and effects on the body can be mild or severe. The three main types of this kind of hypotension are orthostatic hypotension, neurally mediated hypotension (NMH), and severe hypotension associated with shock.

Orthostatic Hypotension

Orthostatic hypotension is low blood pressure that occurs upon standing up from a sitting or lying down position. It can cause a person to feel dizzy, lightheaded or even to faint. It occurs when the body is not able to adjust blood pressure and blood flow fast enough for the change in position. Usually orthostatic hypotension lasts for only a few seconds or minutes after a person stands up. Sometimes a person will need to sit or lie down for a short time while the blood pressure returns to normal.

Orthostatic hypotension can occur in all age groups, but it is more common in older adults, especially those who are frail or in poor health. Orthostatic hypotension can be a symptom of other medical conditions, and treatment generally focuses on treating the underlying condition(s). Some people can have orthostatic hypotension but also have high blood pressure when lying down.

A form of orthostatic hypotension called postprandial hypotension is a sudden drop in blood pressure after a meal. Postprandial hypotension most commonly affects older adults. It also is more likely to affect those with high blood pressure or diseases such as Parkinson disease.

Neurally Mediated Hypotension

In this form of hypotension, blood pressure drops after a person has been standing for a long time. A person may feel dizzy, faint, or sick to the stomach as a result. NMH also can happen when a person faces an unpleasant, upsetting, or frightening situation.

NMH affects children and young adults more often than other age groups. Children often outgrow this form of hypotension.

Severe Hypotension Associated With Shock

Many times people will say a person has "gone into shock" as a result of an emotionally upsetting experience. But to doctors, the word "shock" has a different meaning. Shock is a life-threatening condition in which blood pressure drops so low that the brain, kidneys, and other vital organs can’t get enough blood to work properly. It is different from the other forms of hypotension because blood pressure drops much lower, and it is life threatening if not treated immediately. There are many causes of shock, including major loss of blood, certain severe types of infection, severe burns, severe allergic reactions, and poisoning.

Diagnosis

Hypotension is diagnosed based on your medical history, a physical exam, and results from tests. Your doctor will want to know:

• The type of low blood pressure you have and how severe it is
• Whether an underlying condition is causing the low blood pressure

Specialists Involved

A primary care doctor or specialist may diagnose and treat hypotension. The type of specialist most commonly involved is a cardiologist (heart specialist).

Other specialists also may be involved, such as surgeons, nephrologists (kidney specialists), neurologists (brain and nerve specialists), or others.

Diagnostic Tests

When a person is in shock, someone should call 9–1–1 right away because emergency treatment is needed.

For other types of hypotension, your doctor may order tests to find out how your blood pressure responds in certain situations. The results will help your doctor understand why you’re fainting or having other symptoms.

Blood Tests

During a blood test, a small amount of blood is taken from your body. It’s usually drawn from a vein in your arm using a thin needle. The procedure is quick and easy, although it may cause some short-term discomfort.

Blood tests can show whether anemia or low blood sugar is causing your hypotension.

EKG (Electrocardiogram)

An EKG is a simple test that detects and records the heart’s electrical activity. It shows how fast the heart is beating and the heart’s rhythm (steady or irregular). An EKG also shows the strength and timing of electrical signals as they pass through each part of the heart.

Holter and Event Monitors

Holter and event monitors are medical devices that record the heart's electrical activity. These monitors are similar to an EKG. However, a standard EKG only records the heartbeat for a few seconds. It won't detect heart rhythm problems that don't occur during the test.

Holter and event monitors are small, portable devices. You can wear one while you do your normal daily activities. This allows the monitor to record your heart longer than an EKG can.

Echocardiography

Echocardiography is a test that uses sound waves to create a moving picture of your heart. The picture shows how well your heart is working and its size and shape.

There are several different types of echocardiography, including a stress echocardiogram, or “stress echo.” This test is done as part of a stress test (see below). A stress echo usually is done to find out whether you have decreased blood flow to your heart, a sign of coronary artery disease.

Stress Test

Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise (or are given medicine if you’re unable to exercise) to make your heart work hard and beat fast while heart tests are done.

These tests may include nuclear heart scanning, echocardiography, and magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning of the heart.

Valsalva Maneuver

This is a simple test of the part of your nervous system that controls functions such as your heartbeat and the narrowing and widening of your blood vessels. If something goes wrong with this part of the nervous system, blood pressure problems may occur.

During this test you take a deep breath and then force the air out through your lips. You will do this several times. Your heart rate and blood pressure will be checked during the test.

Tilt Table Test

This test is used if you have fainting spells for no known reason. For the test, you lie on a table that moves from a lying down to an upright position. Your doctor checks your reaction to the change in position.

Doctors use a tilt table test to diagnose orthostatic hypotension and neurally mediated hypotension (NMH). People who have NMH usually faint during this test. The test can help your doctor find any underlying brain or nerve condition.

II.2 Causes

Hypotension is caused by conditions or events that interfere with the body’s ability to control blood pressure.

Orthostatic Hypotension

Orthostatic hypotension has many causes. Sometimes, two or more causes combined will result in hypotension.

Dehydration is the most common cause of orthostatic hypotension. Dehydration occurs when the body loses more water than it takes in. People can become dehydrated because of:

• Not drinking enough fluids
• Fever
• Vomiting
• Severe diarrhea
• Excessive sweating from strenuous exercise

Some medicines used to treat high blood pressure and heart disease can make it more likely that a person will develop orthostatic hypotension. These medicines include:

• Diuretics
• Calcium channel blockers
• Angiotensin-converting enzyme (ACE) inhibitors
• Angiotensin II receptor blockers
• Nitrates
• Beta blockers

Also, medicines used to treat certain other medical conditions, such as anxiety, depression, erectile dysfunction, and Parkinson disease, can make it more likely that a person will develop orthostatic hypotension.

Other substances that can contribute to orthostatic hypotension include alcohol, barbiturates, and some prescription and over-the-counter medicines, when taken in combination with high blood pressure medicines.

Certain medical conditions can increase a person's chances of having orthostatic hypotension. Some of these conditions are:

• Anemia (low red blood cell count).
• Heart conditions leading to heart failure, such as a heart attack or viral infection of the heart. These conditions reduce the heart’s ability to pump enough blood around the body.
• Heart valve disorders.
• Severe infections.
• Endocrine conditions, such as hypothyroidism (underactive thyroid), hyperthyroidism (overactive thyroid), Addison’s disease (adrenal insufficiency), low blood sugar, and diabetes.
• Disorders of the central nervous system, such as Parkinson disease, multiple systems atrophy (Shy-Drager syndrome), and amyloidosis.
• Pulmonary embolism (a sudden blockage in a lung artery).

Finally, other events or conditions that can contribute to orthostatic hypotension include:

• Being out in the heat for a long time
• Having to stay in bed for a long time because of a medical condition
• Being pregnant
• Getting older (the body doesn’t manage changes in blood pressure as well as it gets older)

Neurally Mediated Hypotension

Neurally mediated hypotension (NMH) occurs when the brain and heart don’t communicate with each other properly. For example, when a person stands for a long time, blood begins to pool in the legs. This causes the person’s blood pressure to drop. Instead of telling the brain that blood pressure is low, the body mistakenly tells the brain that blood pressure is high. In response, the brain slows the person’s heart rate, which makes the blood pressure drop even further, causing dizziness and other symptoms.

Severe Hypotension Associated With Shock

Severe hypotension associated with shock can be caused by many conditions or events. Some of these conditions and events also are causes of orthostatic hypotension. The difference in shock is that the blood pressure doesn’t return to normal by itself, and it is at dangerously low levels. Shock is a medical emergency that must be treated immediately.

Certain severe infections can cause shock. This is known as septic shock. This type of shock can occur when bacteria enter the bloodstream. The bacteria release a toxin (a poison) that leads to a dangerous drop in blood pressure.

Shock can be caused by a severe decrease in the amount of blood or fluids in the body. This is known as hypovolemic shock. Hypovolemic shock can happen as a result of:

• Major bleeding on the outside of the body (for example, from an injury)
• Major bleeding inside the body (for example, from a ruptured blood vessel)
• Significant loss of body fluids from severe burns
• Severe inflammation of the pancreas
• Severe diarrhea
• Severe kidney disease
• Excessive use of diuretics

A major decrease in the heart’s ability to pump blood can cause shock. This is known as cardiogenic shock. It can be caused by a heart attack, pulmonary embolism, or arrhythmia.

A sudden and extreme relaxation of the muscles of arteries, which leads to dilation (widening) of the arteries and a drop in blood pressure, can cause shock. This is known as vasodilatory shock. It can happen because of:

• Severe head injury
• Reaction to some medicines
• Liver failure
• Poisoning
• Severe allergic reaction (anaphylactic shock)

II.3 Treatment

Treatment depends on the type of hypotension you have and how severe your signs and symptoms are. The goals of treatment are to relieve signs and symptoms and manage any underlying condition(s) causing the hypotension.

Your response to treatment depends on your age, overall health, and strength. It also depends on how easily you can stop, start, or change medicines.

In a healthy person, low blood pressure without signs or symptoms usually needs no treatment.

If you have signs or symptoms of low blood pressure, you should sit or lie down right away. Put your feet above the level of your heart. If your symptoms don’t go away quickly, you should seek medical care right away.

Orthostatic Hypotension

There are a number of treatments for orthostatic hypotension. If you have this type of low blood pressure, your doctor may advise making lifestyle changes such as:

• Drinking plenty of fluids, like water
• Drinking little or no alcohol
• Standing up slowly
• Not crossing your legs while sitting
• Gradually sitting up for longer periods if you’ve been immobile (not able to move around much) for a long time due to a medical condition
• Eating small, low-carbohydrate meals if you have postprandial hypotension (a form of orthostatic hypotension)

Talk to your doctor about using compression stockings. These stockings apply pressure to your lower legs. They help move blood throughout your body.

If medicine is causing your low blood pressure, your doctor may change the medicine or adjust the dose you take.

Several medicines also are used to treat orthostatic hypotension. These medicines, which raise blood pressure, include fludrocortisone and midodrine. 

Neurally Mediated Hypotension

If you have neurally mediated hypotension (NMH), you may need to make lifestyle changes. These may include:

• Avoiding situations that trigger symptoms. For example, don’t stand for long periods of time, and avoid frightening or upsetting situations.
• Drinking plenty of fluids, like water.
• Increasing salt intake
• Learning to recognize symptoms that occur before fainting, and taking action to raise blood pressure (crossing the legs and squeezing them together or lying down).

If medicine is causing your low blood pressure, your doctor may change the medicine or adjust the dose you take. He or she also may prescribe a medicine to treat NMH.

Children with NHM often outgrow it.

Severe Hypotension Associated With Shock

Shock is a life-threatening emergency. People who have shock usually need to be treated in a hospital or by emergency medical personnel. If a person has signs or symptoms of shock, someone should call 9–1–1 right away.

The goals of treating shock are to:

• Restore blood flow to the organs as quickly as possible to prevent organ damage
• Find and reverse the cause of shock

Special fluid or blood injected into the bloodstream is often used to restore blood flow to the organs. Medicines can be used to raise blood pressure or make the heartbeat stronger. Depending on the cause of the shock, other treatments, such as antibiotics or surgery, may be needed.